/*
 * Copyright (C) 2013 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.math;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import java.util.Random;

/**
 * Benchmarks for various ways of writing the expression {@code foo + ((bar < baz) ? 1 : 0)}.
 *
 * @author Louis Wasserman
 */
public class LessThanBenchmark {
    static final int SAMPLE_SIZE = 0x1000;
    static final int SAMPLE_MASK = 0x0FFF;

    @Param("1234")
    int randomSeed;

    int[] xInts;
    int[] yInts;

    long[] xLongs;
    long[] yLongs;

    int[] constant;

    private static final long NONNEGATIVE_LONG_MASK = 0x7FFFFFFFFFFFFFFFL;

    @BeforeExperiment
    void setUp() {
        Random random = new Random(randomSeed);
        xInts = new int[SAMPLE_SIZE];
        yInts = new int[SAMPLE_SIZE];
        xLongs = new long[SAMPLE_SIZE];
        yLongs = new long[SAMPLE_SIZE];
        constant = new int[SAMPLE_SIZE];
        for (int i = 0; i < SAMPLE_SIZE; i++) {
            xInts[i] = random.nextInt(Integer.MAX_VALUE);
            yInts[i] = random.nextInt(Integer.MAX_VALUE);
            xLongs[i] = random.nextLong() & NONNEGATIVE_LONG_MASK;
            yLongs[i] = random.nextLong() & NONNEGATIVE_LONG_MASK;
            constant[i] = random.nextInt();
        }
    }

    @Benchmark
    int branchFreeLtIntInlined(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            int x = xInts[j];
            int y = yInts[j];
            int z = constant[j];
            tmp += z + ((x - y) >>> (Integer.SIZE - 1));
        }
        return tmp;
    }

    @Benchmark
    int branchFreeLtInt(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            int x = xInts[j];
            int y = yInts[j];
            int z = constant[j];
            tmp += z + IntMath.lessThanBranchFree(x, y);
        }
        return tmp;
    }

    @Benchmark
    int ternaryLtIntAddOutsideTernary(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            int x = xInts[j];
            int y = yInts[j];
            int z = constant[j];
            tmp += z + ((x < y) ? 1 : 0);
        }
        return tmp;
    }

    @Benchmark
    int ternaryLtIntAddInsideTernary(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            int x = xInts[j];
            int y = yInts[j];
            int z = constant[j];
            tmp += (x < y) ? z + 1 : z;
        }
        return tmp;
    }

    @Benchmark
    int branchFreeLtLongInlined(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            long x = xLongs[j];
            long y = yLongs[j];
            int z = constant[j];
            tmp += z + (int) ((x - y) >>> (Long.SIZE - 1));
        }
        return tmp;
    }

    @Benchmark
    int branchFreeLtLong(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            long x = xLongs[j];
            long y = yLongs[j];
            int z = constant[j];
            tmp += z + LongMath.lessThanBranchFree(x, y);
        }
        return tmp;
    }

    @Benchmark
    int ternaryLtLongAddOutsideTernary(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            long x = xLongs[j];
            long y = yLongs[j];
            int z = constant[j];
            tmp += z + ((x < y) ? 1 : 0);
        }
        return tmp;
    }

    @Benchmark
    int ternaryLtLongAddInsideTernary(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & SAMPLE_MASK;
            long x = xLongs[j];
            long y = yLongs[j];
            int z = constant[j];
            tmp += (x < y) ? z + 1 : z;
        }
        return tmp;
    }
}
